Electrical liquid heater



Feb. 20, 19.23. 1,446,317 w. PENzoLD vELECTRICAL LIQUID HEATER Filed MayZ, 1922 2 sheets-sheet l Feb. zo, 1923. 1,446,317 W. PEvNZOLD 2 ELECTRICAL LIQUID HEATER Filed May 22, 1922 2 Sheets-sheen 2 Maf/erg PatentedFeb. 20, 1923.

UNITED STATESv 1,446,317 PATENT OFI-leef WILHELM PENZOLD, O HANOVER,GERMAY, ASSIGNOR T0 WIDERSTAND AKTIENr GESELLSCHAFT FRELEKTRO-WRME-TECHNIK, OF HANOVER, GERMANY, A COM* PANY OF GERMANY.

ELECTRICAL LIQUID HEATER.

Application ined May 22,`

over, Germany. have invented certain new' and useful Improvements inElectrical Liquid Heaters, of which the followingisa specification.

This invention relates to electrical liquid heaters wherein the liquidconstitutes a resistance and is applicable to water heaters or steamgenerators.

In order that the invention may be' more clearly understood referencewill be hereinafter made 4to the accompanying drawings whereon Fig. l isa diagram illiistrating a known type ot electric heater; Fig. 2illustrates one example of my invention in cross-section withaccompanying diagram and Fig. 3 is a vertical sectional view-ot ,-Fig.2. y,

In the concentric arrangement of two metallic cylindrical electrodes asin Fig. l and as adopted in electric Water heaters or steam generators,the current flows in a radial direction from the inner to the outercylinder, as indicated by the dotted lines. The maximum current densityand consequent maximum Voltage drop occurs on the surface or" the innercylinder, vThe hyperbolle curve et volts per centimeter in Fig. l showsthe variation ot the Voltage drop as the distance increases from theinner cylinder. These values apply where the radius or" the innercylinder rzl cm., the ratio ot the radius of the outer cylinder, r2,

r to the radius of the inner cylinder, 7:5

efficiency of the heater depends on the characteristics of the volt percin, curve.

It is well known that in electric steam generators having concentricelectrodes,

overloading causes momentary vaporization ot the liquid close to theinner electrode, transforming the steam `generator into a'n intcrruptersimilar in principle to the Nehiielt and Simon interrupter.

li' lt represents the resistance or 1 cc. of

1922. Serial No. 562,731.

water, the output transformed into heat in this Volume of water isrepresented by the formula vol ts per cin2 The curve of watts per ccm.in Fig l represents this value where RzlOOO ohms. rlhe vratio of theoutput in ccm. at the inner electrode to the output at the outerelectrode is equivalent to to l, that is, to thesquare of the ratio ofthe radii.

The formation ot steam bubbles further reduces the efficiency. Thebubbles of course form in much greater quantity against the innercylinder owing to the greater watts per ccm. and by decreasing thecross-section involve-increased current density and consequent increasedvoltage drop and decreased eiiiciency. For these reasons the concentricarrangement must not be run at too high a load.

The present invention has for its object to overcome the drawbacks ofthe concentric arrangement and for this purpose the surtace of the outercylinder is equal or approximately equal to that ot the inner cylinderso that the current density is the same at both electrodes. This may beei?- Liected by covering part oi the surface off the outer electrodewith insulation.

Fig. 2 shows one example in which a` is the inner electrode t', 52, Z13and )i are the surfaces of the outer cylinder actually availn able tothe current and equal in area to a. rllhe rest or the surface ot theouter vcylinder is covered with nsi'ilation c', c2, c3, and o1. By thisarrangement the current is distributed as indicated in dotted lines inThe curves 'for Volts per cm. and watts per ccm. are also shown for aVoltage diti'erence ot 500 volts with 0:1 ein. and

2 T7: 5 ein.

A comparison or the two diagrams shows that the maximum value of wattsper ccm. in Fig. l is only reached by the arrangement according to Fig.2 with more than twice the main current voltage. Thus the arrangementaccord-ing` to Fig. 2 approxii mates the ideal condition in which thecurrent is unitormiy distributed over thespace between the twoelectrodes,

In order to avoid a short circuiting effect n the current distribution,the base or ends of the boilerA may be also cov .i d with in sulation. Y

Fig. 3l illustrates a constructional form of the heater, in which thebottom e is covered by insulation f and the tubular body (l of .theboiler is closed at the top by a coverv 71:, and in which the innerelectrode a is connected to a binding post h on the cover by aconducting rod g.

The insulation used for covering the surface of the electrodes alsoserves Simultaneously to protect the boiler from the heat.

Claims:

1. An electrical liquid heater having con centric electrodes andinsulation covering 'a part of the inner surface of the outer elec`trode to leave an uncovered outer electrode surface equal orsubstantial-ly equal to that WILHELM PENZOLD.

